Steep terrain can be a hindrance on Mars as well as Earth. NASA's Mars rover Opportunity recently encountered a band of darker rocks inside "Victoria Crater" that increased in steepness.

Though its steepness put this rock outcrop out of bounds for the rover, it was important to scientists because changes in the rocks suggest changes in the past environment. Detailed images of nearby cliffs in "Victoria Crater" indicate they may have been part of an ancient dune field. Scientists guided Opportunity to a more accessible exposure of the same band of rocks for a closer look.